"I am often asked how radio works. Well, you see, wire telegraphy is like a very long cat. You yank his tail in New York and he meows in Los Angeles. Do you understand this? Now, radio is exactly the same, except that there is no cat." : Albert Einstein

Tuesday, July 17, 2012

If you happen to use the AppleTV with Netflix you may have been suffering from the same frustration as I have in the last few months. Despite a 12Mbps internet connection, good WiFi signal strength and Apple Airport Extreme Wireless-N router I have been plagued with the dreaded pause & buffer while watching Netflix movies during prime time. This simply doesn't occur while watching the same videos, at the same time, on my iPad, iPhone, Mac desktop or PC laptop.

Perhaps the most aggravating part of the experience is that I think I have the problem worked out but I am unable to do anything about it.

It appears that Netflix have the ability to dynamically change the bandwidth used by each customer during peak times as well as the ability to set the bandwidth used by a customer based on the customers own available bandwidth. These mechanisms, working together, allow the largest number of customers access to Netflix videos and movies during peak times with only a slight degradation in video quality. Although I'm against throttling when used indiscriminately, this particular application makes sense, the alternative is that customers find themselves unable to watch movies during peak times or suffer timeouts or impossibly slow access. This arrangement works well on devices that use an up-to-date Netflix client or browser access, however the Apple TV is, at the moment, where is goes all pear shaped.

I noticed that the AppleTV Netflix app would never dynamically alter the bandwidth used by a streaming video once it had started playing, in fact it seems as though it always plays the video at the highest quality possible even when it would involve a significant time spent buffering before playing. If Netflix does dynamically reduce bandwidth during peak times it would make sense that the AppleTV, unwilling or unable to downshift to a lower bitrate, would start to suffer stalls and constant buffering as it starved for data. Needless to say, this results in a horrible experience for the viewer.

Something that was mentioned on the Apple forums also supported this theory. It was noted that changing the DNS entries could resolve this issue ... at least for a short while. This would make sense if the DNS server pointed to a different Netflix server address where there was less load, and therefore less throttling at that moment.

There are currently 45 pages of users complaints In just one thread alone on the Apple community forums and, as far as I can tell, nobody from apple has made a public announcement that addresses this issue. This doesn't come as a surprise as Apple is typically reluctant to discuss individual bugs and fixes in an open forum.

While people may patiently wait for fixes on iPhone & iPads, they may not wait for Apple to get their act into gear when there are better, less expensive, alternatives available that work well. I am seriously considering swapping out my AppleTv for a Roku 2 XD which, aside from working well with Netflix, has access to much more programming. It would be a shame to lose the ability to mirror the iPad or iPhone display but for the few times I used that feature, compared to all the times I want to sit down and watch a movie at night without having it pause randomly, the Roku wins.

Perhaps Apple will release a fix tomorrow ... perhaps next month. Its not knowing where they are at that cause so much frustration in the user community & that is not a good thing for a company that prides itself on making things that "just work"

Monday, July 9, 2012

Despite my interest in boat-anchors I do find myself peeking 'over the wall' from time to time and taking a look at new and emerging technologies. After several demonstrations from friends I had become convinced of the incredible potential of software defined radios and even found thinking about owning one ... one day.

Perhaps the best known SDR in amateur radio circles are the FLEX rigs from FlexRadio. I had the chance to see a FLEX-3000 in use during Winter Field Day 2011 and had to admit that, barring the lack of knobs & dials, it was a very impressive rig!

One thing stopped me from running out and buying one straight away was the cost and perhaps the notion that once the new had worn off I would regret the significant outlay required to own the blue box. So, I shelved the idea of owning an SDR and found other things to occupy my time.

This changed when a post on www.reddit.com/r/amateurradio/ mentioned an unmodified digital TV receiving USB device that had been used as a software defined receiver in the 60MHz - 1.7GHz range. The best part was the cost, around $20 for most examples of this kind of device. Finally software & commodity hardware had come together to deliver useful receiver that everyone can afford.

The nuts and bolts:

There are specific parts required to put together your own $20 SDR but I will document what I used to get mine running and hopefully you can follow along.

Hardware: The device that I used was a Ezcap EZTV668 DVB-T Digital TV USB 2.0 Dongle purchased from DealExtreme. The part was shipped from Asia and I gather from reading else ware that DealExtreme is a middleman and not the actual supplier. Be prepared to wait a while if ordering from this supplier, my Ezcap took about 3 weeks to arrive but I have heard that a month or more is not uncommon.

The upside is that shipping is free and your purchase involves 0% tax, this really IS a $20 SDR.

This particular DVB-T dongle uses the RTL2832U chip which is required for use as an SDR, other dongles with this chip may work but if it does not have the RTL chip it will NOT work currently.

Software (Linux) : After poor results with the software running on MS Windows I moved across to Linux and got it working well there. I can't point you to a single howto for this because I used several different guides and tried a few things before it started working. The most helpful, and probably all you really need, are the build-gnuradio script which gets hardware support and gnu-radio running and the "Getting Started With RTL-SDR" page by Tom Nardi which covers installing Gqrx. All the software used is in development and requires familiarity with the command line to install and use at the moment.

Software (Windows) : I had another shot at getting the MS Windows software running and stumbled across the excellent website http://rtlsdr.org. Rtlsdr.org mentions using a new version of SDR# software which worked very well!

I would recommend following the instructions under the Windows Software section, this had me up and running in a matter of minutes. Follow the instructions EXACTLY, I made life hard on myself by not paying attention to details and I think was responsible for my earlier issues.

Going further - Antenna : The stock antenna that is supplied with the Ezcap EZTV668 is sufficient for testing but you'll want to add something a bit more substantial for regular use. You may even want to remove the existing (hard to find) antenna connector from the board and install a standard connector and a less flimsy metal casing. This will help with RF shielding and temperature stability.

If you are going to use a larger antenna, especially an outside antenna, you'll want to check to make sure a protection diode has been fitted to the input. The Ezcap EZTV668 is a very inexpensive device and others have found units in which the protection diode was not fitted to save costs.

Going further - 160M - 6M ? : I've just seen an interesting blog post titled FunCube Upconverter where the author, George Smart, has built a converter allowing the reception of 160M - 6M using the FunCube dongle. The FunCube is functionally the same as the RTL dongles available for $20. For any home brewers out there this could be a great project as George has included all the details including schematics and board artwork required to build the converter.

I've had a lot of fun using the $20 SDR to listen to AM aircraft traffic, local repeaters, emergency services and amazingly good quality broadcast FM stereo programming. Its easy to see, with an SDR, just how wide a radio broadcaster is transmitting and move your filter bandwidth to match.

Hopefully this is just the beginning of inexpensive SDR hardware that the radio community can re-purpose and re-engineer.

Sunday, July 8, 2012

It took a little while but I finally got the video for the Katy Amateur Radio Society summer field day together. I didn't shoot as much video or as many photographs this year as I actually spent time a fair amount of time operating for a change!

Hopefully it will still be an entertaining, if short, reminder of those two days in June.